- The name of the system include directory has changed to not
  include the minor version inforamtion.  Update the hacky computation
  of this name for copying the Checked C files to that location.
- FileCheck now complains about unused check-prefix
  arguments when checking test results. This uncovered a bunch
  of errors in our dynamic_checking tests with incorrect check prefixes
  (the test wasn't checking its results properly).
- Clang's defaults have changed, so now a bunch of warnings are now
  errors.  These include things that Checked C complained about
  anyway, such as missing prototypes, incorrect function pointer casts,
  and so on.  The warnings being converted to errors affected some of
  our tests. We included clang's messages because they occurred on the
  same line as our errors.
- A few error messages have change format.
- Disabled the typechecking\no_prototype_functions.c test on Windows.
  It seems to cause the compiler to loop due to some changes in the
  internal representation of types. It might loop on Linux, I haven't
  checked.

Testing results:

Here are the results from running check-checkedc on Windows:
  Unsupported:  6
  Passed     : 82
  Failed     : 11